Project Summary Neuropathic pain caused by trauma and surgery is a major clinical problem and remains difficult to treat. Neuronal plasticity at the spinal cord level is fundamentally important to the development of neuropathic pain caused by nerve injury. N-methyl-D-aspartate receptors (NMDARs) are glutamate-gated cation channels critically involved in central sensitization and maintenance of neuropathic pain. However, the molecular mechanisms underlying potentiated NMDAR activity in the spinal dorsal horn after nerve injury remain poorly understood. ?2?-1, commonly known as a subunit of voltage-activated calcium channels, is upregulated in the dorsal root ganglion and spinal dorsal horn after nerve injury. Although ?2?-1 upregulation contributes to neuropathic pain, little is known about the mechanisms through which ?2?-1 is involved in neuropathic pain development. In our preliminary studies, we found that ?2?-1 physically interacted with NMDAR subunits and that siRNA knockdown of ?2?-1 profoundly attenuated spinal cord NMDAR activity increased by nerve injury. Furthermore, gabapentin treatment interrupted the ?2?-1 and NMDAR association and normalized nerve injury?induced potentiation of spinal NMDAR activity. In this proposal, we will use a multidisciplinary approach to test our central hypothesis that nerve injury?induced ?2?-1 upregulation critically contributes to potentiation of spinal NMDAR activity and development of neuropathic pain by physically interacting with NMDARs and that gabapentinoids attenuate nerve injury?induced pain hypersensitivity and NMDAR activity at the spinal cord level by disrupting the ?2?-1?NMDAR physical association. Our project is expected to generate substantial new information to unravel a novel function of ?2?-1 as a potent regulatory protein of NMDARs and to identify the important role of ?2?-1?NMDAR complexes in the development of neuropathic pain. Because our studies will provide new molecular insight into mechanisms of neuropathic pain and gabapentinoid actions, our project is highly innovative and underscores a major conceptual advance in understanding the molecular composition, heterogeneity, and function of native NMDARs and synaptic plasticity. We expect that these new findings will significantly advance our understanding of the molecular mechanisms of neuropathic pain and lead to the development of new strategies to treat chronic neuropathic pain.